MODIFICATION OF SILICON SURFACES WITH H2SO4-H2O2-HF AND HNO3-HF FOR WAFER BONDING APPLICATIONS

Two combinations of oxidizing and etching agents, H2SO4:H2O2:HF and HN O3:HF, have been used to modify silicon surfaces prior to wafer bondin g. The chemical oxide thickness can be adjusted between 0 and 10 Angst rom by tuning the HF content of the mixtures. Using x-ray photoelectro n spectroscopy it was found that the chemical composition of the surfa ces can also be affected. Hydroxyl groups, fluorine, and hydrogen are terminating species that can be obtained by the described procedures. Both the described cleaning procedures permit hydrophilic bonding, giv ing a high room temperature bond strength with a minimum of interfacia l oxide. The bond between a mainly fluorine-terminated or a mainly OH terminated surface and a hydrogen-terminated surface is no stronger th an the bond between two hydrogen-terminated surfaces.